This invention relates generally to the field of photonic crystals. More particularly, this invention relates to a photonic crystal structure and a method for layer-by-layer fabrication of such crystal structure.
Photonic crystals are being actively pursued as components in optical networks, such as wavelength-division multiplexing applications. Examples of potential applications are as filters, mirrors, waveguides, and prisms. Added functionality could allow the crystals to be used in other applications such as frequency-tunable filters, optical switches, chemical and biological recognition systems, as well as other potential applications.
Three dimensional (3-D) photonic crystals have been made using a number of approaches. One common approach uses a colloidal technique that allows a distribution of spheres (e.g. microspheresxe2x80x94typically spheres approximately in the range of 90 nm to several microns in diameter) to settle out of solution into a bulk 3-D crystal. A similar approach uses the surface tension of a moving liquid/gas interface, created by either by pulling a substrate out of a liquid or by evaporating the liquid, to create a 3-D crystal made of up microspheres. Both techniques result in a close-packed structure of identical spheres. More complex structures are possible if differently sized spheres are used, but there is very little external control over the crystallization process and the resulting structure. The spheres can be made with a number of different materials, with polystyrene a common example, and the components are uniform in size and composition. Crystals fabricated using this technique are mechanically unstable unless a matrix such as a polymer matrix is used between the spheres to mechanically reinforce the structure.
The present invention relates generally to photonic crystals. Objects, advantages and features of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the invention.
In general terms, without any intention of limiting the invention, the present invention, in certain embodiments, relates to a technique which can be used to fabricate photonic crystals in a controlled, layer-by-layer manner. This allows control over parameters not possible with traditional colloidal techniques and permits novel crystal structures to be created.
In one exemplary embodiment consistent with the present invention a three dimensional photonic crystal is fabricated starting with a templated substrate that is exposed to a plurality of first microspheres made of a first material, the first material being of a type that will bond to the templated substrate and form a self-passivated layer of first microspheres to produce a first layer. The first layer is exposed to a plurality of second microspheres made of a second material, the second material being of a type that will bond to the first layer and form a self-passivated layer of second microspheres. This layering of alternating first and second microspheres can be repeated as desired to build a three dimensional photonic crystal of desired geometry.
A method of fabricating a photonic crystal, consistent with certain embodiments of the present invention involves providing a templated substrate; and exposing the templated substrate to a plurality of first microspheres made of a first material, the first material being of a type that will bond to the templated substrate and form a self-passivated layer of first microspheres to produce a first layer. A second layer can be created by exposing the first layer to a plurality of second microspheres made of a second material, the second material being of a type that will bond to the first layer and form a self-passivated second layer of second microspheres.
Another method of fabricating a photonic crystal consistent with certain embodiments of the present invention involves providing a templated substrate; exposing the templated substrate to a plurality of first microspheres made of a first material, the first material being of a type that will bond to the templated substrate and form a self-passivated layer of first microspheres to produce a layer of microspheres; modifying the first layer of microspheres to permit the first layer of microspheres to bond with other microspheres to thereby produce a bondable layer; exposing the bondable layer to a plurality of second microspheres to form a second layer of microspheres. The second layer of microspheres can be made of the first material or of a second material.
A photonic crystalline structure consistent with certain embodiments of the present invention has a templated substrate processed to bond preferentially to a first material in selected areas. A first layer of first microspheres, the first layer being one microsphere deep, is made of a material that bonds to the selected areas of the templated substrate. A second and subsequent layers can be added wherein the second and subsequent layers of microspheres can be made of the first material or of a second material.
The above summaries are intended to illustrate exemplary embodiments of the invention, which will be best understood in conjunction with the detailed description to follow, and are not intended to limit the scope of the appended claims.